// Copyright 2018 the V8 project authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "src/base/bounded-page-allocator.h"

namespace v8 {
namespace base {

    BoundedPageAllocator::BoundedPageAllocator(v8::PageAllocator* page_allocator,
        Address start, size_t size,
        size_t allocate_page_size)
        : allocate_page_size_(allocate_page_size)
        , commit_page_size_(page_allocator->CommitPageSize())
        , page_allocator_(page_allocator)
        , region_allocator_(start, size, allocate_page_size_)
    {
        CHECK_NOT_NULL(page_allocator);
        CHECK(IsAligned(allocate_page_size, page_allocator->AllocatePageSize()));
        CHECK(IsAligned(allocate_page_size_, commit_page_size_));
    }

    BoundedPageAllocator::Address BoundedPageAllocator::begin() const
    {
        return region_allocator_.begin();
    }

    size_t BoundedPageAllocator::size() const { return region_allocator_.size(); }

    void* BoundedPageAllocator::AllocatePages(void* hint, size_t size,
        size_t alignment,
        PageAllocator::Permission access)
    {
        MutexGuard guard(&mutex_);
        CHECK(IsAligned(alignment, region_allocator_.page_size()));

        // Region allocator does not support alignments bigger than it's own
        // allocation alignment.
        CHECK_LE(alignment, allocate_page_size_);

        // TODO(ishell): Consider using randomized version here.
        Address address = region_allocator_.AllocateRegion(size);
        if (address == RegionAllocator::kAllocationFailure) {
            return nullptr;
        }
        CHECK(page_allocator_->SetPermissions(reinterpret_cast<void*>(address), size,
            access));
        return reinterpret_cast<void*>(address);
    }

    bool BoundedPageAllocator::AllocatePagesAt(Address address, size_t size,
        PageAllocator::Permission access)
    {
        CHECK(IsAligned(address, allocate_page_size_));
        CHECK(IsAligned(size, allocate_page_size_));
        CHECK(region_allocator_.contains(address, size));

        if (!region_allocator_.AllocateRegionAt(address, size)) {
            return false;
        }
        CHECK(page_allocator_->SetPermissions(reinterpret_cast<void*>(address), size,
            access));
        return true;
    }

    bool BoundedPageAllocator::FreePages(void* raw_address, size_t size)
    {
        MutexGuard guard(&mutex_);

        Address address = reinterpret_cast<Address>(raw_address);
        size_t freed_size = region_allocator_.FreeRegion(address);
        if (freed_size != size)
            return false;
        CHECK(page_allocator_->SetPermissions(raw_address, size,
            PageAllocator::kNoAccess));
        return true;
    }

    bool BoundedPageAllocator::ReleasePages(void* raw_address, size_t size,
        size_t new_size)
    {
        Address address = reinterpret_cast<Address>(raw_address);
        CHECK(IsAligned(address, allocate_page_size_));

        DCHECK_LT(new_size, size);
        DCHECK(IsAligned(size - new_size, commit_page_size_));

        // Check if we freed any allocatable pages by this release.
        size_t allocated_size = RoundUp(size, allocate_page_size_);
        size_t new_allocated_size = RoundUp(new_size, allocate_page_size_);

#ifdef DEBUG
        {
            // There must be an allocated region at given |address| of a size not
            // smaller than |size|.
            MutexGuard guard(&mutex_);
            CHECK_EQ(allocated_size, region_allocator_.CheckRegion(address));
        }
#endif

        if (new_allocated_size < allocated_size) {
            MutexGuard guard(&mutex_);
            region_allocator_.TrimRegion(address, new_allocated_size);
        }

        // Keep the region in "used" state just uncommit some pages.
        Address free_address = address + new_size;
        size_t free_size = size - new_size;
        return page_allocator_->SetPermissions(reinterpret_cast<void*>(free_address),
            free_size, PageAllocator::kNoAccess);
    }

    bool BoundedPageAllocator::SetPermissions(void* address, size_t size,
        PageAllocator::Permission access)
    {
        DCHECK(IsAligned(reinterpret_cast<Address>(address), commit_page_size_));
        DCHECK(IsAligned(size, commit_page_size_));
        DCHECK(region_allocator_.contains(reinterpret_cast<Address>(address), size));
        return page_allocator_->SetPermissions(address, size, access);
    }

    bool BoundedPageAllocator::DiscardSystemPages(void* address, size_t size)
    {
        return page_allocator_->DiscardSystemPages(address, size);
    }

} // namespace base
} // namespace v8
